The new Caution Trespass (Epoxy PVC construction) is a bit harsh on the heels/knees, and I was thinking of getting something more flexible. I suppose the other option is to find a cheap short board on craigslist and dump 2oz of glass onto the top deck.

I like to put an anti-fatigue gym mat on the deck of my boards. It is the closest thing to riding a soft surfboard. Helps to prevent heal dents on normal surfboards. It is much cheaper than a full deck pad. And it doesn't get slippery like wax after a few hours of riding.